发送带有MailMessage的MailMessage作为附件

Question

I am attempting to send an email that has emails as attachments. I am able to send an email and it comes through with the attachments but I get the following message in outlook when trying to open any of the attachments. I think this has to do with the encoding of the email attachment

:

MailMessage mm1 = new MailMessage();
mm1.IsBodyHtml = true;
mm1.Body = "Body for person to approve";
mm1.Subject = "Home Owner's Insurance Policy";
mm1.From = new MailAddress("insurance@email.com", "SAHL");
mm1.ReplyTo = new MailAddress("insurance@email.com");
mm1.To.Add("ross.kriel@email.co.za");


foreach (NewBusinessData item in lData)
{

    MailMessage mm = new MailMessage();
    mm.IsBodyHtml = true;
    mm.Body = HTMLBody;
    mm.Subject = "Home Owner's Insurance Policy";
    mm.From = new MailAddress("insurance@email.com", "SAHL");
    mm.ReplyTo = new MailAddress("insurance@email.com");

    byte[] thisAttachment;
    thisAttachment = Common.Attach(Settings.Default.NewBusinessCSFDataFileWriterPath +                item.PolicyNumber + "_" + item.MortgageLoanAccountNumber + ".pdf");

     Stream ClientPDF = new MemoryStream(thisAttachment);

     Attachment attStaticPDF = new Attachment(StaticPDF, "Home Owner's Insurance Policy.pdf");

     Attachment attClientPDF = new Attachment(ClientPDF, item.PolicyNumber + ".pdf");
     mm.Attachments.Add(attStaticPDF);
     mm.Attachments.Add(attClientPDF);

     Assembly assembly = typeof(SmtpClient).Assembly;
     Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
     MemoryStream stream = new MemoryStream();

     ConstructorInfo mailWriterContructor =    mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
     object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
     MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
     sendMethod.Invoke(mm, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null);

    stream.Position = 0;
    Attachment emailAtt = new Attachment(stream, "Home Owner's Insurance Policy.msg");

    mm1.Attachments.Add(emailAtt);
 }

SmtpClient smtp1 = new SmtpClient();
smtp1.Host = "IPHost";
smtp1.Port = 25;
smtp1.UseDefaultCredentials = true;
smtp1.EnableSsl = false;
try
{
    smtp1.Send(mm1);
}
catch (Exception exd)
{
    Console.WriteLine(exd.ToString());
}

Answer 1

Outlook's msg format is a binary file format - the MailWriter writes the mail in a manner that an SMTP server would expect to recieve the data (per RFC 821) - ie a plaintext format. As such, the file you're attaching isn't in the format that Outlook is expecting.

Answer 2

So at the end of the day it was the Transfer Encoding that caused the problem. Specifying it as Eight bit and ensuring the attachment also had the right media type solved the problem.

MailMessage mm1 = new MailMessage();
mm1.IsBodyHtml = true;
mm1.Body = ReportMsgBody;
mm1.Subject = "Home Owner's Insurance Policy Proofs: " + lData.Select(x => x.FileName).First();
mm1.From = new MailAddress("insurance@email.com", "FromName");
mm1.ReplyTo = new MailAddress("insurance@email.com");
mm1.To.Add(receiver.EmailAddress);

foreach (NewBusinessData item in lData)
{
    MailMessage mm = new MailMessage();
    mm.IsBodyHtml = true;
    mm.Body = HTMLBody;
    mm.Subject = "Home Owner's Insurance Policy";
    mm.From = new MailAddress("insurance@email.com", "FromName");
    mm.ReplyTo = new MailAddress("insurance@email.com");
    mm.To.Add(item.EmailAddress);

    byte[] thisAttachment;
    thisAttachment = Common.Attach(Settings.Default.FileWriterPath + item.PolicyNumber + "_" + item.MortgageLoanAccountNumber + ".pdf");
    Stream ClientPDF = new MemoryStream(thisAttachment);
    Attachment attClientPDF = new Attachment(ClientPDF, item.Pr + ".pdf", "application/pdf");
    mm.Attachments.Add(attClientPDF);

    byte[] thisAttachment2;
    thisAttachment2 = Common.Attach(Settings.Default.StaticAttatchmentPath + "Home Owner's Insurance Policy.pdf");
    Stream StaticPDF = new MemoryStream(thisAttachment2);
    Attachment attStaticPDF = new Attachment(StaticPDF, "Home Owner's Insurance Policy.pdf", "application/pdf");
    mm.Attachments.Add(attStaticPDF);

    Assembly assembly = typeof(SmtpClient).Assembly;
    Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
    MemoryStream stream = new MemoryStream();

    ConstructorInfo mailWriterContructor = mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
    object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
    MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
    sendMethod.Invoke(mm, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null);

    stream.Seek(0, SeekOrigin.Begin);
    Attachment emailAtt = new Attachment(stream, "Home Owner's Insurance Policy", "message/rfc822");
    emailAtt.TransferEncoding = System.Net.Mime.TransferEncoding.EightBit;
    mm1.Attachments.Add(emailAtt);
}